I was thinking maybe a cookie could be set.
This is for my stock photography web site -
http://photosofplants.com - and I've made the "wish list" into a "light box," a common feature on this type of site to help customers select images for purchase.
Not needing to register or log in would make it more user-friendly.
There is a product that does offer this capability -
http://www.lightboxphoto.com/ - and when you return the lightbox is still there so this must be done with a cookie.
Anyway thanks for your response!